Positron emission tomography has been shown to be useful in the diagnosis of both cardiac and neurologic disorders. The goal of this project is the development of a positron emission tomograph which, due to its simple design, will be more suitable for routine clinical application than most research oriented positron tomographs. The single crystal positron tomography will have a cylindrical scintillation detector to which approximately 160 photomultipliers are coupled. It will have a diameter of 60 cm with an axial field of view of approximately 12 cm, thus making it suitable for brain imaging. Phase I of the proposal consists of a feasibility study which will hopefully lead to the construction of a complete scanner as part of phase II.